[quote]ORIGINAL: Gry101

The pumps that I am using work off of the crank case pressure. So in theory, they should pump fuel every revolution and not be dependent on the vibrations.

Maybe the design of the pumps are not capable of the high RPM pulsations? There is mass in terms of fuel and in the pump parts, at some point ( rpm) this mass can act as a dampener to itself.
I think you do best in removing the pumps as the other posters suggests.
Go step by step for trouble shooting on ground:
First separate tanks with separate pressure at carb level, then play around one step at the time with tank height/one tank setup and so on.....


Fuel supply need to be free flowing into the carb - Make sure you have the largest high quality fuel line dimension as the carb has a bigger than usual bore and therefore less natural fuel suction.
Check that you have clips on the fuel line to keep the fittings at the carb and tank air-leak free

all the best